U.S. patent application number 15/318126 was filed with the patent office on 2017-04-20 for structural yielding fuse.
The applicant listed for this patent is CAST CONNEX CORPORATION. Invention is credited to Constantin CHRISTOPOULOS, Juan-Carlos DE OLIVEIRA, Michael GRAY.
Application Number | 20170107734 15/318126 |
Document ID | / |
Family ID | 54934587 |
Filed Date | 2017-04-20 |
United States Patent
Application |
20170107734 |
Kind Code |
A1 |
GRAY; Michael ; et
al. |
April 20, 2017 |
STRUCTURAL YIELDING FUSE
Abstract
A yielding fuse for use in a brace assembly includes a first
body portion configured to be connected at one end to a side of a
brace member of the brace assembly, and a second body portion
configured to be connected at one end to another side of the brace
member of the brace assembly. The first and second body portions
are positioned so as to be disposed on opposite sides of an axis
defined by the brace member, with each of the first and second body
portions further including a base displaced from the axis, a
plurality of yielding arms extending from the base towards the axis
and at least a first connecting plate rigidly connecting the first
body portion to the second body portion. Preferably, a second
connecting plate is also provided.
Inventors: |
GRAY; Michael; (Toronto,
CA) ; DE OLIVEIRA; Juan-Carlos; (Toronto, CA)
; CHRISTOPOULOS; Constantin; (Toronto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CAST CONNEX CORPORATION |
Toronto |
|
CA |
|
|
Family ID: |
54934587 |
Appl. No.: |
15/318126 |
Filed: |
June 18, 2014 |
PCT Filed: |
June 18, 2014 |
PCT NO: |
PCT/CA2014/050572 |
371 Date: |
December 12, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 7/128 20130101;
E04B 2001/2415 20130101; F16F 1/00 20130101; E04B 1/2403 20130101;
E04B 1/36 20130101; E04H 9/0237 20200501; E04B 2001/2496 20130101;
E04H 9/028 20130101; E04B 2001/2442 20130101; E04H 9/021 20130101;
E04H 9/024 20130101 |
International
Class: |
E04H 9/02 20060101
E04H009/02; E04B 1/36 20060101 E04B001/36; E04B 1/24 20060101
E04B001/24 |
Claims
1. A yielding fuse for use in a brace assembly comprising: a first
body portion configured to be connected at one end to a side of a
brace member of the brace assembly; a second body portion
configured to be connected at one end to another side of the brace
member of the brace assembly; said first and second body portions
positioned so as to be disposed on opposite sides of an axis
defined by the brace member; each of said first and second body
portions further including a base displaced from the axis; a
plurality of yielding arms extending from said base towards the
axis; a first connecting plate rigidly connecting said first body
portion to said second body portion.
2. The yielding fuse according to claim 1, wherein said plurality
of yielding arms includes a bottom portion attached to said base
and a top portion distal from said bottom portion.
3. The yielding fuse according to claim 2, wherein said plurality
of yielding arms are tapered such that said bottom portion is
thicker than said top portion.
4. The yielding fuse according to claim 2, further comprising a
means for connecting said first and second body portions to a
beam-column intersection of the brace assembly.
5. The yielding fuse according to claim 4, wherein said means for
connecting comprises a splice plate connected to the beam-column
intersection and a first support plate connected to the splice
plate; said first support plate connected to at least two of said
plurality of yielding arms to connect said splice plate to said
first and second body portions.
6. The yielding fuse according to claim 5, further comprising a
second support plate; wherein said first support plate and said
second support plate are configured, sized and otherwise
dimensioned to be connected to opposite ends of said top portion of
said plurality of yielding arms on each of said first and second
body portions.
7. The yielding fuse according to claim 1, further comprising a
second connecting plate rigidly connecting said first body portion
and said second body portion.
8. The yielding fuse according to claim 7, wherein said first
connecting plate is connected to a front surface of said first and
second body portions and said second plate is connected to a back
surface of said first and second body portions.
9. The yielding fuse according to claim 8, wherein said first
connecting plate is generally parallel and optionally co-planar
with a front surface of the brace member and said second connecting
plate is generally parallel and optionally co-planar with a back
surface of the brace member.
10. The yielding fuse according to claim 8, wherein said first and
second connecting plates are welded to said first and second body
portions, respectively.
11. A brace assembly comprising at least one brace member defining
an axis and connected to a structural frame by a yielding fuse;
wherein said yielding fuse comprises: a first body portion
configured to be connected at one end to a side of said brace
member; a second body portion configured to be connected at one end
to another side of said brace member; said first and second body
portions positioned so as to be disposed on opposite sides of said
axis; each of said first and second body portions further including
a base displaced from the axis; a plurality of yielding arms
extending from said base towards the axis; a first connecting plate
rigidly connecting said first body portion to said second body
portion.
12. The brace assembly according to claim 12, wherein said
plurality of yielding arms includes a bottom portion attached to
said base and a top portion distal from said bottom portion.
13. The brace assembly according to claim 13, wherein said
plurality of yielding arms are tapered such that said bottom
portion is thicker than said top portion.
14. The brace assembly according to claim 12, further comprising a
means for connecting said first and second body portions to a
beam-column intersection of the brace assembly.
15. The brace assembly according to claim 14, wherein said means
for connecting comprises a splice plate connected to the
beam-column intersection and a first support plate connected to the
splice plate; said first support plate connected to at least two of
said plurality of yielding arms to connect said splice plate to
said first and second body portions.
16. The brace assembly according to claim 15, further comprising a
second support plate; wherein said first support plate and said
second support plate are configured, sized and otherwise
dimensioned to be connected to opposite ends of said top portion of
said plurality of yielding arms on each of said first and second
body portions.
17. The brace assembly according to claim 11, further comprising a
second connecting plate rigidly connecting said first body portion
and said second body portion.
18. The brace assembly according to claim 17, wherein said first
connecting plate is connected to a front surface of said first and
second body portions and said second plate is connected to a back
surface of said first and second body portions.
19. The brace assembly according to claim 18, wherein said first
connecting plate is generally parallel and optionally co-planar
with a front surface of the brace member and said second connecting
plate is generally parallel and optionally co-planar with a back
surface of the brace member.
20. The brace assembly according to claim 18, wherein said first
and second connecting plates are welded to said first and second
body portions, respectively.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to structural building
members, and more particularly to a connecting element for
controlled yielding of structural members under seismic, or
similar, loading.
BACKGROUND OF THE INVENTION
[0002] Many building structure designs include the use of diagonal
braces to provide lateral stability, especially for the purpose of
increasing the lateral stiffness of the structure and reducing the
cost of construction. In such bracing systems it is known that one
or more sacrificial yielding fuse elements may be implemented in
order to dissipate seismic input energy in the event of dynamic
loading, such as during a severe seismic event. Such sacrificial
yielding fuse elements can be designed to provide improved seismic
performance and reduced seismic loads when compared to traditional
lateral load resisting systems.
[0003] Many prior art systems require a buckling restraining
apparatus used in conjunction with a yielding member, and make use
of axially yielding members, whereas it would be advantageous to
use flexural yielding elements as they are less prone to fracture
caused by excessive inelastic straining.
[0004] U.S. Pat. No. 4,823,522 to White, U.S. Pat. No. 4,910,929 to
Scholl and U.S. Pat. No. 5,533,307 to Tsai and Li all describe
steel yielding fuse elements that are placed at the centre of a
beam and are used to add damping and stiffness to a seismically
loaded moment resisting frame. The damping elements are generally
formed with steel plates that are cut into triangular shapes and
welded or bolted to a rigid base. Also, these elements are
generally installed at the centre of the upper brace in and
inverted V-type braced frame. Thus the yielding of these elements
is controlled by the inter-story displacement of the frame.
However, a yielding element that was linked to the brace elongation
rather than the inter-story displacement would integrate more
easily with current construction practices.
[0005] Another prior art fuse system, the EaSy Damper, uses a
complex fabricated device to improve the seismic performance of
brace elements by replacing axial yielding and buckling of the
brace with combined flexural and shear yielding of a perforated,
stiffened steel plate. The shapes of these plates do not result in
constant curvature of the yielding elements and thus lead to
undesirable strain concentrations.
[0006] Both of the aforementioned prior art systems require
painstaking cutting and welding fabrication. Furthermore, the
limited geometry of currently available rolled steel products
restricts the potential geometry of the critical yielding elements
of such devices.
[0007] Having greater control of the geometry of the flexural
yielding elements permits control of not only the force at which
the fuse yields, but also the elastic and post yield stiffnesses of
the fuse as well as the displacement associated with the onset of
fuse yielding. With casting technology a better performing fuse can
be designed and manufactured. Also, free geometric control would
enable the design of a part that would more easily integrate with
existing steel building erection and fabrication practices than the
prior art.
[0008] Another prior art system described in U.S. Pat. No.
8,683,758 to Christopoulos et al. describes a yielding fuse which
includes elements that yield flexurally when a brace member moves
in an axial direction, with the bracing assembly under either
tensile or compressive loading conditions. The yielding fuse is
connected co-axially with diagonal braces in a building structure.
The non-yielding elements of this yielding fuse, the elastic
portions, must be designed to resist axial, flexural, and shear
forces. The end of each yielding arm is connected via bolts to a
fabricated plate assembly, which is in turn connected to a
structural gusset plate. At the other end of the fuse, the elastic
portions are connected to the structural brace member. The
Christopoulos et al. fuse requires substantial cast material to be
provided in the elastic portions, and the design is fairly complex
owing to the necessity to design for flexural, shear, and axial
forces.
[0009] It is therefore an object of the invention to provide an
improved yielding fuse.
SUMMARY OF THE INVENTION
[0010] According to one embodiment of the invention, there is
provided a yielding fuse for use in a brace assembly including a
first body portion configured to be connected at one end to a side
of a brace member of the brace assembly and a second body portion
configured to be connected at one end to another side of the brace
member of the brace assembly. The first and second body portions
are positioned so as to be disposed on opposite sides of an axis
defined by the brace member. Each of the first and second body
portions further include a base displaced from the axis, a
plurality of yielding arms extending from the base towards the
axis, and a first connecting plate rigidly connecting the first
body portion to the second body portion.
[0011] According to one aspect of this embodiment, the plurality of
yielding arms includes a bottom portion attached to the base and a
top portion distal from the bottom portion.
[0012] According to another aspect of this embodiment, the
plurality of yielding arms are tapered such that the bottom portion
is thicker than the top portion.
[0013] According to another aspect of this embodiment, there is
further provided a means for connecting the first and second body
portions to the beam-column intersection of a building frame.
[0014] According to another aspect of this embodiment, the means
for connecting includes a splice plate connected to the beam-column
intersection and a first support plate connected to the splice
plate; the first support plate connected to at least two of the
plurality of yielding arms to connect the splice plate to the first
and second body portions.
[0015] According to another aspect of this embodiment, there is
further provided a second support plate; wherein the first support
plate and the second support plate are configured, sized and
otherwise dimensioned to be connected to opposite ends of the top
portion of the plurality of yielding arms on each of the first and
second body portions.
[0016] According to another aspect of this embodiment, there is
further provided a second connecting plate rigidly connecting the
first body portion and the second body portion.
[0017] According to another aspect of this embodiment, the first
connecting plate is connected to a front surface of the first and
second body portions and the second plate is connected to a back
surface of the first and second body portions.
[0018] According to another aspect of this embodiment, the first
connecting plate is generally parallel and optionally co-planar
with a front surface of the brace member and the second connecting
plate is generally parallel and optionally co-planar with a back
surface of the brace member.
[0019] According to another aspect of this embodiment, the first
and second connecting plates are welded to the first and second
body portions.
[0020] According to a second embodiment of the invention, there is
provided a brace assembly including at least one brace member
defining an axis and connected to a structural frame by a yielding
fuse. The yielding fuse is substantially as has been summarized
with respect to the first embodiment, or described elsewhere in
this application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments will now be described, by way of example only,
with reference to the attached Figures, wherein:
[0022] FIG. 1 is a front view of a brace assembly using the
yielding fuse of the invention.
[0023] FIG. 2 is an exploded view of the yielding fuse of the
invention.
[0024] FIG. 3 is a front view of one body portion of the fuse of
FIG. 2.
[0025] FIG. 4 is a top view of the body portion of FIG. 3.
[0026] FIG. 5 is a bottom view of the body portion of FIG. 3.
[0027] FIG. 6 is a right side view of the body portion of FIG.
3.
[0028] FIG. 7 is a left side view of the body portion e of FIG.
3.
[0029] FIG. 8 is a perspective view of an assembled yielding fuse
according to the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] The improved structural yielding fuse of the invention is an
improvement to the earlier described U.S. Pat. No. 8,683,758 to
Christopoulos et al., the contents of which in their entirety are
herein incorporated by reference. However, the yielding fuse as
herein described includes improvements which are generally
applicable in the art and includes advantages over the prior art
including one or more of using less material in construction, ease
of attachment to other elements in the structural frame, and
replacability following an earthquake. Other advantages may also
become apparent to one skilled in the art.
[0031] With reference now to FIG. 1, there is shown a typical
braced frame 10 including a plurality of frame members 15 and at
least one brace member 20. The yielding fuse 25 to which the
invention is primarily directed connects the brace members 20 to a
beam-column intersection of the braced frame. The brace member 20
defines an axis along which the yielding fuse 25 is arranged
coaxially, such that during normal loading conditions, or no-load
conditions, the yielding fuse 25 functions as an extension of the
brace member in a manner indistinguishable therefrom. The yielding
fuse 25 is designed to only yield under exceptional loads, such as
those that occur during major seismic events. The operation and
purpose of yielding fuses in general is described in the
aforementioned Christopoulos et al. publication, and are thus not
described in detail in this application. In brief, however, the
yielding fuse is designed and adapted to yield when the brace
assembly is subjected to exceptional loads, such as those that
occur during major seismic events. The yielding fuse, being
designed to yield, protects the structural integrity of other
elements of the braced frame by isolating the location where the
braced frame first yields. The brace member 20 is any typical
structural steel shape (W-Shape, Hollow Structural Section, etc.).
Brace members of this sort, as well as their profiles and shapes,
are generally known in the art and the teachings of this invention
may be applied to a variety of forms and arrangements of the brace
members and braced frames.
[0032] One embodiment of the yielding fuse 25 is shown in FIG. 2.
The yielding fuse 25 includes a first body portion 30 and a second
body portion 35. The first and second body portions 30 and 35 are
generally symmetrical, and are optionally identical to one another.
FIGS. 5 to 7 show various views of an individual first or second
body portion, to which reference may also be made. Each of the
first 30 and second 35 body portions have one end 40 configured to
be connected to a side or end 50 of the brace member (as shown in
FIG. 1). In the preferred embodiment, the ends 40 include a
connecting face for attachment of the body portions via bolts to
the brace member. Other connections are also possible, for example
welding to the brace member 20. It is preferred, however, that the
attachment to the brace member 20 is a removable one. This permits
ready replacement of the yielding fuse if needed. The first 30 and
second 35 body portions are preferably connected opposite to one
another so that the first 30 and second 35 body portions are
symmetrical about the axis defined by the brace member 20 when the
fuse is in its fully assembled state and connected to the braced
frame 10.
[0033] Generally the description that follows will refer to
features of the first body portion 30, however they are equally
applicable to the second body portion 35 as the two are either
symmetric or identical to each other. The body portion 30 has a
base 45 which is displaced from the axis defined by the brace
member 20, and a plurality of yielding arms 55 extending from the
base 45 towards the axis, and more explicitly towards the axis of
the brace member 20. However, the yielding arms 55 are eccentric
with the axis of the brace member 20
[0034] The plurality of yielding arms 55 generally include a bottom
portion 60 attached to the base 45 and a top portion 65 distal from
the bottom portion 60 in a direction closer to the brace member
axis. The yielding arms 55 are preferably tapered such that the
bottom portion 60 is thicker than the top portion 65. Such tapering
encourages yielding along the entire length of the yielding arm
when the yielding fuse is activated. It is also contemplated that
the yielding arms may be tapered along their height, such that the
bottom portion and the top portion have the same thickness, however
the thickness decreases along the profile of the yielding arms when
viewed from the side, as in FIG. 3. The yielding arms may also be
tapered in both directions.
[0035] Of importance to the invention is the inclusion of a force
equilibrating means to connect the first and second body portions,
and thereby link the mechanical response of the body portions when
the yielding fuse is loaded. By connecting the body portions,
bending moments and shear forces generated by the eccentricity of
the yielding arms are internally balanced, and thus the force
governing the design of the elastic portions of the fuse is
generally axial in nature. The yielding arms can thus be produced
using less material and ultimately be lighter than the teachings of
the aforementioned Christopoulos et al. application. Furthermore,
the force equilibrating means is designed to eliminate movement of
each of the body portions and yielding arms with respect to one
another during extreme loading, thus resulting in a more
predictable yielding of the fuse. Ancillary advantages include
simplifying the manner in which the yielding fuse can be connected
to the brace member since the connection between the yielding fuse
and the brace member has to account for axial forces only. In the
prior art, accommodations had to be made to account for axial,
shear, and flexural forces both in the design of the elastic
portions of the fuse and in the connections to the brace
member.
[0036] In order to accomplish the aforementioned force
equilibrating, there is provided a first connecting plate 70
rigidly connecting the first body portion 30 to the second body
portion 35. There is also preferably provided a second connecting
plate 75 connecting the first body portion 30 to the second body
portion 35 on an opposite side of the yielding fuse. The connecting
plates 70, 75 may be steel plates of sufficient strength and
rigidity that when coupled to the body portions results in a rigid
and uniform yielding fuse including the connecting plates 70, 75
and the first and second body portions 30, 35.
[0037] The first connecting plate 70 is preferably connected to the
first body portion 30, and the second connecting plate 75 connected
to the second body portion 35 by aligning an underside of the
respective connecting plate 70 or 75 with the top and bottom
surfaces of the first 30 and second 35 connecting plates,
respectively, and welding the connecting plates 70 or 75 to the top
and bottom surfaces of the first 30 and second 35 body
portions.
[0038] In order to connect the yielding fuse 25 to the brace frame
10, and thereby connect the brace 20 to the brace frame 10, a
splice plate 85 is provided, and connected to the first 30 and
second 35 body portions, preferably by virtue of being connected to
the yielding arms 65 of the first 30 and second 35 body portions.
As it is desirable to have the yielding of the yielding arms 65 be
internally balanced, and specifically that corresponding yielding
arms on the first 30 and second 35 body portions yield in a
corresponding manner, the splice plate 85 is provided with a pair
of support plates 90, spaced in a direction perpendicular to the
brace member to accommodate the size of each of the top portions 65
of the yielding arms 55. The support plates 90 are axially centered
with respect to the splice plate 85, with corresponding thru holes
on either side of the splice plate. The support plates 90 may then
be bolted to the top portion 65 of the yielding arms through the
bolt holes shown on the top portion 65 of the yielding arms 55. The
splice plate 85 may be connected to the brace frame in ways that
are known in the art, for example, by being welded or bolted to a
gusset plate as shown in FIG. 1. Thus, the yielding arms 55 of each
of the first 30 and second 35 body portions are directly connected
to the brace frame 10, and yielding of the yielding arms 55 becomes
linked to the mechanical yielding of the brace member to which the
yielding arms are connected. Thus, the respective elements can be
sized and designed such that the yielding arms yield under
catastrophic yielding conditions, as described earlier, rather than
having the brace member yield.
[0039] When assembled, it is also preferred that the first
connecting plate 70 is generally parallel and optionally co-planar
with a front surface of the brace member and the second connecting
plate 74 is generally parallel and optionally co-planar with a back
surface of the brace member. This provides for a compact yielding
fuse that does not protrude from the profiles of the brace member
to a significant extent in the direction perpendicular to that of
the brace member. This permits the yielding fuse to be implemented
within the wall space of a building structure, with minimal
obstruction to other elements.
[0040] Furthermore, by virtue of having the first and second
connecting plates connected to each of the first and second body
portions, the bending moments and shear forces generated by the
eccentricity of the yielding arms under load conditions become
internally balanced.
[0041] FIG. 8 shows a fully assembled yielding fuse as herein
described. As can be seen, the yielding fuse is more compact than
prior art solutions. In addition, the unitary structure which binds
the yielding arms of both the first body and the second body, on
either side of the brace member provides for equilibrated forces
within the yielding fuse, thus resulting in primarily axial loading
of the body portions during load conditions.
[0042] It will be appreciated by those skilled in the art that the
yielding devices of the present invention may be cast or fabricated
from various different materials. In particular, any suitable cast
material is possible, especially castable steels. For example, ASTM
A958 Grade SC8620 Class 80/50 steel, with Si content less than
0.55% by weight, would be a suitable material for the yielding
devices. Also suitable would be ASTM A216/A216M WCB and ASTM
A352/A352M LCB. Using these grades ensures that the yielding device
is a weldable base metal. Different alloys and different types of
steel may be used for the casting depending on the properties that
are required for the particular application.
[0043] The above-described embodiments are intended to be examples
of the present invention and alterations and modifications may be
effected thereto, by those of skill in the art, without departing
from the scope of the invention that is defined solely by the
claims appended hereto.
* * * * *